Process and apparatus for digesting fibrous material



P. W. NEIL July 21, 1931.

A PROCESS AND APPARATUS FR DIGESTING FIBROUS MATERIAL A 2 Sheets-Sheet Filed April 14, 1930 ami mi* 4July 21, 1931.

P. w. NEIL 1,815,576

v PROCESS AND APPARATUS FOR DIGESTING FIBROUS MATERIAL 4 Filed'ApIiil 14, 1950 2 Sheets-Sheet 2 I Hummm.

E E U KY l Qw.\\ n. @NJN @u NN MN mi mim@ Ik Nw Jrrgnf/Yel S@ mw a @y Patented July 21,1931 Y UNITED STATES PAT ENT OFFICE y PEIRCY W. NEIL, OF QUEBEC lCITY, QUEBEC, CANADA, ASSIGNOR TO THOMAS L. DUNBAR, OF WATEIRJJOWN,v NEW'VYORK lrnocsss AND APPARATUS For. DIGESTTNG Finnous MATERIAL appucation 'mea Alan 14,

rlhis invention relates to an improved method and apparatus for digesting fibrous material to be used in making paper pulp or the like.

The primary object of the invention is to provide a novel syst-em for relieving the di gesters of gases. vapor or liquor, and for utilizing these fluids to preheat and precondition acid liquor that is subsequently em' 1o ployed for digesting the raw material in an- A relief fluids' to means for recovering the SO2 or* the heat units of the fluid, or both the SO2 and the heat units. In one proposal, an injector is arranged at the top of each digester, and acid liquor is circulated through these injectors for the purpose of immediately mixing the hot fluids from the digesters with the cold liquor, and `such proposal necessitates the use of an injector for each digester, as well as three pumps for the entire recovery system. Furthermore, as the pressure varies inthe different digesters during the cooking periods, suchiiuctuation will affect the pressure existing in the relief'line, and prevent uniform conditions from being maintained. In another prior proposal, a single syphon or injector is used for passing lowpressure relief fluids from the digesters to a liquor storage tank or the like, and in that system,

40 the high pressure relief fluids pass directly from-the digesters to a high pressure accumulator. Owing to the variations of pressure in the line, and the fact that the pressure gradually buildsup in the accumulator, the 4.5, relief fluid in the high pressure header must overcome the varying pressure as it builds up in the accumulator, and this tends to prevent uniform conditions being maintained in the system.' Furthermore, in such system,

a large pump must be employed for a lshort 1930. Serial No. 444,186.V i

inate the disadvantages of such systems by employing a special apparatus, and so controlling the same that a single small pump operating continuously to force liquor from the storage tank into the accumulator, will act to maintain uniform pressure in the high pressure header, and also function to relieve the accumulator of gases.

My. improved system may not alone be used in connection with a high pressure header and a high pressure accumulator, but may be so arranged that the pumped acid liquor from the storage tank will lirst act to main-A tain a uniform pressure in the low pressure header, and to relieve gases from a low pressure accumulator, and maythen be forced by a second small pump through a passageway into the high. pressure accumulator; the liquor in travelling through said passageway functioning to maintain uniform pressure conditions in the high pressure header, and acting to relieve the high pressure accumulator of gases which are very strong, and which will therefore enrich and heat up the iquor goingjto the high pressure accumuator. v

With the foregoing objects outlined and with other objects in view which will appear as the description proceeds, the invention consists in the novel featureshereinafter de' scribed in detail, illustrated in the accom- Apanying drawings, and more particularl pointed out in the appended claims. Referring to the drawin s,

Fig. l is an elevation o a portion of an apparatus with which my method may be practiced. o

Fig. 2 is atop plan view of a modified` apparatus for the same general purpose, and Fig. 3 is an elevation of the apparatus shown in Fig. 2.

In the embodiment of the invention illustrated in Fig. 1, 5 indicates conventional presexample, a T-connection 9, that is joined to a pipe 10 that has a control valve 11, and leads to the bottom portion of a high pressure accumulator 12.

The digesters are also provided with valved lowpressure relief branches 13 which are connected to a low pressure header 14 that is.`

joined to a pipe 15 that extends downwardly into an acid liquor storage tank 16, and terminates in a conventional perforated distributor 17 located in the lower portion of tank 16, and designed to distribute any fluids from the pipe 15 uniformly in the cold liquor contained in the storage tank. The tank 16 is closed, but as low pressure fluids are released for a short part of the cooking operation only, such fluid will not materially heat up the liquor in the tank, but will tend to enrichthe same to some extent. A

Acid liquor is supplied to the tank by way of a valved pipe 18, and is continuously forced from the same by a small pump 19 which forces the liquor through a conduit 20 provided with a check valve 21 that prevents any fluid from flowing through the pipe 20 toward thejpump.

Pipe 2O terminates in a nozzle 22 whlch leads into an injector tube 23, the latter terminating in an injector nozzle 24 which extends into the T-connection 9. From the foregoing it will be understood that as the pump 19 continuously operates to force a jet of chemical liquor through the nozzle 24, and into the pipe 10, suction will constantly be exerted in the high pressure header 8, so that regardless of the variation of pressure existing in the different digesters, and in the high Vpressure accumulator, the pressure in the -header 8 will be uniformly maintained, and

the stream of liquor mixing with the high vpressure relief f'luidsinr the T-connection 9, will tend to absorb gases and to impound the heat units from the relief fluids, so that the acid liquor on its way to the accumulator, will not only be strengthened, but will be heated.

Due to the introduction of heated acid liquoil into the high pressure accumulator, it is manifest that the pressure will build up in the latter, and gases will gather in the accumulator above the liquor. In accordance with my invention, such gases are relieved by the use of the pumped stream of liquor flowing to the nozzle 24, and for this purpose, the accumulator is provided at its top with a relief pipe 25 that leads to a side branch 26 of the injector tube 23,V and is furnished with a check valve 27 that prevents any flow of fiuid through the conduit 25 toward the accumulator. It will therefore be seen that the j'et of liquor from the nozzle 22 will exert suction in the pipe 25 so as to constantly relieve 'the accumulator of gas which is mixed with the acid liquor and returned to the bottom of the accumulator.

In a system in accordance with my invention, while the contents of one digester are being cooked, and the contents of the other digesters are in various stages of cooking, the high pressure and side relief gases, vapors and liquid relieved from the digesters, will be induced to flow to the pipe 10 by the continuously moving stream of liquor from the pump 19, and consequently, the high pressure accumulator may be completely filled with preheated and strengthened liquor during the cooking period of a digester, and this preheated and preconditioned liquor can then be forced'into a digester which has just been filled with chipsl or other hrous material. For this purpose, a valved pipe 28 at the bottom ofthe accumulator is joined to a pump 29 that leads into a header 30, that is connected by branch valved pi es 3l to the lower ends of the'digesters. bviouslyfwhen the valve 11 is closed, and valve 28 is opened, the contents of the accumulator may be forced bythe pump' 29, to a digester containing raw fibrous material, and in this Way, the preconditioned and preheated liquor may be employed in the. next cooking operation;

Each digester is provided with the usual valved outlet pipe 32, leading to the blowpit, not shown, and each digester will have the usual steam inlet pipes, but as these elements form no part of the present invention, it is unnecessary to refer further to the same. It is believed from the above description and the drawings, that those skilled in the art will recognize that my system or'hookup is an improvement over those heretofore used, and it will be noted that it includes having the over gas line 25 from the top of the accumulator, connected into the high pressure header, as shown at 9, and then, in addition, the line 20 for filling the accu mulator, brought into an injector, so that the pumped liquor puts a partial suction on the top -of the accumulator, and the high pressure header, the arrangement being such that the relief fluids are thoroughly mixed with the pumped liquor.

An advantage is obtained by such systems, as compared with the previous-prop,osals, due to the condensing effect of the cold storage acid liquor on the hot gases, vapors and liquors from the digesters, and consequently, the pressure in the high pressure header is reduced, and at the same-time, the digesters are permitted to relieve against a practically constant pressure. Without the injec-` which* means that the rate of flow from a di- ;gester is not constant. Vhereas, with, myv lmethod, there is a constant relief but a progressive increase of the amount of liquid and gas discharged from' the digester until practically the end of the cooking operation.

A The pressure against which the digesters resame time that gases are being relieved into the accumulator 12, the latter isbeing filled with acid, and the'iow of cold acid from the storage tank] is regulated, so that by the time it is necessary to fill the neXt digester in the line, the accumulator is full of hot strong acid. This, of course, varies in different plants in accordance with the 'number of digesters cooking, an-d the length of the cook. As before stated, instead of running a large pump for a few minutes tofill the accumulator right after it has been emptied, as was the custom in the past, I employ a much smaller pump running continuously.

Moreover, as compared with the method of handling digesters in which an injector nozzle is arranged at each dig-ester, the system illustrated in Fig. 1 requires only two injec# tor nozzles, one'to take care of the overhead gas from the accumulator 12, and the other to handle the gas, vapor and liquor from the digesters, j

In the embodiment of the invention shown inFigs. 2 and 3, I use the same principle of operation, but employ injectors in connectionwith the low pressure header, as well as with l the high pressure header, and I use a low pressure accumulator, as well as a highpressureaccumulator, and pump preheated and preconditioned liquor from the low pressure accumulator to the high pressure accumulator.

Referring to these figures of the drawings, 50 indicates the digesters, each having at its top portion a valved -high pressure relief branch 51, and a valved' low pressure relief branch 52. These branches leading to the high pressure header 53 that is provided with any suitable form of injector fitting, such as a T-connection 54, joined to a down pipe 55l that empties into ahigh pressure accumulator 56, and is equipped with a control valve 57.

Valved low pressure relief branches 58 connect the upper portions of the digesters with a low pressure header59, which, in this in stanceis provided with -a T-connection 60 that communicates with the lower end of a low pressure accumulator 61 by means of a valved conduit 62.

In this modification, the cold acid liquor from a storage tank 6355s forced'by a continuously operating small pump 64 through a pipe 65 having an interposed check valve 66 that prevents any reverse flow of fluid through the pipe. A nozzle 67 forms the terminal of the pipe 65, anddischarges into an injector tube 68 .that terminates in a second -nozzle 69, leading into` the T-connection 60. Obviously, cold liquor continuously forced by the pump 64, will act to condense low pressure gases in connection 60, and pipe 62, so that a uniform pressure will be maintained in the 'low pressure header. 'At the same time,

any gas gathering inthe accumulator 61, will be withdrawn by the flowing stream of liquor `tlhrou gh the conduit 70, which joins the top bf this accumulator to a side inlet branch 71 of the injector tube 18, and is equipped with a check valve 72 which prevents reverse How. 'So far, it will be'seen that .the Vcold liquor flowing from the pump 64 to the'pipe 62, is

caused by the injector nozzles 69 and 67 to exert suction in the header 59, and in the pipe 70, so that any gases or other fluids'induced to flow in this. way, are mixed with the cold liquor and fed to the accumulator 61 and at the same time, the digesters or low pressure relief, release against aA uniform pressure maintained in the header 59.

The liquor which is partially preconditioned and preheaterd in this way, is forced from the bottom of the low pressure accumulator by means of a pump 73 through a conduit 7 4 which is provided with a check valve 75 and terminates in a nozzle 76, located in an injector tube 77. Said tube also has a nozzle 7 8 which leads into the T'connection 54 of the high pressure header, so that liquor c ontinuously forced by the pump 7 3, acts to condense relief fluids from the high pressure header, and to thus maintain a substantially uniform pressure in the header 53; the relief fluids being mixed with the liquor and heating the latter as the mixture flows through the pipe 55 into the high pressure accumu lator 56. For the purpose of relieving the latter of'gases, a pipe 79 connects the top ofV the same with a side branch 8() of the injector tube 77, this pipe also having a check valve 81 to prevent reverse flow.

It will be manifest from the foregoing that if the pumps 64 and 7 3 are relatively small andy continuously operated, the injector nozzle 69 will function to cause condensation of low pressure gases and vapors in the low pressure header 59, and to thus maintain a substantially constant pressure in that header, while any gases tending to rise in the ac cumulator 6.1 will be sucked out due to the nozzle 67, and will thus be mixed with the flowing liquor and returned through the pipe 62 to the low pressure accumulator. Then, the liquior forced bythe pump 7 8, in leaving the nozzle 78, will act .to condense high pressure and side relief fluids from the digesters, and to thus hold a substantially uniformpressure in the header 53, and at the same time, the nozzle 76 will act to withdraw gases from the high pressure accumulator.

When accumulator 56 Has been filled with hot strengthened acid liquor in this way, such liquor is Withdrawn through a(pipe 82 and forced by a pump 83, intoa header 84 that is connected by valv'ed branch pipes 85 to the lower portions` of the digesters. It is apparent that in this way a digester which has been charged with fibrous material, may be completely `filled with strengthened heated acid liquor to be used for digesting purposes.

In general, due to mill conditions, if it is desirable to blow a. digester at approximately 40 pounds pressure, the arrangement disclosed in Fig. -1 will be used, whereas, if it is desirable to bring the pressure on the di gesters down to from 20 pounds to zero, before blowing, the arrangement illustrated in Figs. 2 and 3 will be necessary. Furthermore, if a plant is located where odors are objectionable, the second, arrangement is the preferable one.

While I have disclosed what I now consider to be preferred embodiments of the invention in such manner that the same maybe readily understood by those skilled in the art, I am aware that changes may be made in the details disclosed, Without departing from the spirit of the invention, as expressed in the claims. i

What I claim and desire to secure by Letters Patent is:

1. In the digestin of .fibrous material, owing a stream of chemical liquor to an ac cumulator chamber, utilizing the flowing stream to withdraw gases and vapors from said chamber, and mixing the withdrawn gases and vapors with the flowingstream.

2. In the digestion of fibrous material, forcing a confined stream of chemical liquor into an accumulator chamber, utilizing the flowing stream to withdraw gases and vapors from said chamber, and mixing the withdrawn gases and vapors with the flowing stream.

3. In the digestion of fibrous material, owing a stream of chemical liquor to an accumulator chamber, utilizing the flowing stream to Withdraw gases and vapors from said chamber, mixing the withdrawn gases and vapors with the stream of liquor flowing -to the chamber, and owing the chemical liquor from said chamber into a digester containing brous material.

4. In the digestion of Vfibrous material, flowing a stream of chemical liquor to an accumulator chamber, utilizing `the owing stream to maintain a substantiallyuniform pressure in a digester header, and mixing the iowing stream with relief liquor from the header while the stream is on its way to the accumulator chamber.

5. In the digestion of fibrous material, flowing a stream of chemical liquor to an accumulator chamber, utilizing the flowing stream to maintain a substantially uniform pressure in a digester header, 'mixing the flowing stream with relief liquor from the header while the stream is on its Way to the accumulator chamber, and feeding strengthened and heated liquor from the accumulator chamber to a digester.

6. In the digestion of fibrous material, releasing hot fiuid from a number of digesters into a header, flowing a stream of chemicalliquor to an accumulator chamber, passing the stream of liquor on its way to the accumulator, through a restricted passageway and utilizing suction exerted by the liquor stream in passing through said restricted passageway to maintain a substantially'umform pressure in said header.

7. In the digestion of fibrous material, re

leasing hot iuid from a number'of digesters 'condense gases and vapors of the relief fluid,

and to carry the condensates to the accumulator chamber. 0

8. In the digestion of fibrous material, flowing a stream of chemical liquor to an acv cumulator chamber, passing the stream on its way to the accumulator chamber through a restricted passageway, and utilizing suction thus created to withdraw gaseous fluid from the upper portion of the accumulator chamber, passing the stream through a second restricted passageway, and utilizing suction created by the passage of the liquor through the second restricted passageway to exert suction in a digester header.

9. In the digestion of fibrous material, releasing pressure fluid from a number of digesters into 'a header, injecting substantially cold acid liquor into said header at one point and thereby condensing the gases and vapors of the relief uid, and maintaining a substantially uniform pressure in said header, and passi-'ng the resulting mixture from the point where the liquor is injected, into an accumulator chamber.

10. In the digestion of fibrous material, releasing pressure fluid from' a number of digesters into a header, injecting substantially cold acid liquor into said header at one point and thereby condensing the gases and vapors of the relief fluid and maintaining a substan# tially uniform pressure in said header, passing the resulting mixture .from the point where the liquor is injected, into an accumulator chamber, and utilizing the force of the flowing `stream of liquor on its way to the accumulator chamber to withdraw gases passing the resulting mixture from the point Vgesters into a header,

Where the liquor is injected, into an accumu- -lator chamber, and' passing liquor thus heated and strengthened from the accumulator chamber into a digester containing fibrous material. l*

12. In the digestion of fibrous material,

' passing relief gases, vapors and liquid from digesters at various stages, of the cooks therein, into a header, continuously injecting 4substantially cold acid liquor into said header at one point and thus condensing gases and vapors in the relief fluid and maintaining the pressure in the header substantially constant, passing the mixtureof gases, vapors and liquor from the point of injection into an accumulator and thereby gradually filling said `accumulator With strengthened and preheated acid liquor, and :finally forcing the heated strengthened liquor from the accumulator into a digester which has just been charged with fibrous material.

13. In the digestion of fibrous material, releasing gases, vapors and liquid from the upper portions of digesters into a header, flowing a stream of substantially cold acid liquor to an accumulator chamber, mixing said i stream on its way to the accumulator chamber with the gases,'vapors and liquid from the header, and thereby condensing the gases and vapors and thus maintaining a substantiallyuniform pressure in said header, also utilizing the flowing stream to Withdraw gases and vapors from the accumulator chamber and to mix the last mentioned gases and vapors with the flowing stream, and passing pre'- conditioned -aci-d liquor from the accumulator chamber into a digester containing i'ibrous material'.

14. In the digestion' of fibrous material,

discharging gases, vapors and liquid into a header simultaneously from the upper portions of'a number of digesters While brous material is undergoing-cooking in said digesters by the use of chemical liquor, maintaining a substantially uniform pressure'in.

said header by injecting a stream of substantially cold acid liquor into the header at one point, and mixing this acid liquor stream with the relief gases, vapors and liquid, and thereby condensingv said gases and vapors, and passing the mixture from the point of injection into an accumulator chamber.

15. In the digestion of fibrous material, flowing a stream of chemical liquor to a low pressure accumulator chamber, utilizing suction created by said flowing stream to withdraw low pressure reliefffluid from the upper portion of a digester, and to mix said low pressure relief iiuid with the flowing streamwhile the latter is on its Way to the low pressure accumulator, flowing liquor thus preconditioned vfrom the low pressure accumulator in the form of a second stream f to a high pressure accumulator, and utilizing suction created by the second stream to condense gases and vapors from a digester header and to mix the last mentioned gases j and vapors with the second stream While 'that Vpressure relief fluid with the flowing stream while the latter is on its Wayto the. low pressure accumulator, flowing liquor thus preconditioned from the low pressure accumulator in the form of a second stream to a high pressure accumulator., utilizing suction created by the second stream to condense gases and vapors from a ldigester header and to mix the last mentioned gases and vapors with the second stream While that stream is flowing to the high pressure accumulator, and utilizing suction created by one of said streams to. Withdraw gas from the top of one of said accumulators and vto mix said gas with the last mentioned stream.

17. In the digestion of fibrous material, {iowing a stream of chemical liquorto a low pressure accumulator chamber, utilizing suction created by said 4flowing stream to Withdraw low pressure relief fluid from the upper portion of a digester, and to mix saidlow pressure relief fluid with the flowing stream While the latter is on its way to the low pressure accumulator, flowing liquor thus preconditioned from the lowpressure accumulator in the form of a second stream to a high pressure accumulator, utilizing suction created by the second stream to condense gases and vapors from a digester header and to mix the last mentioned gases and vapors with the second stream While that stream is flowing to the high pressure accumulator, and flowing preheated and preconditioned liquorfrom the high pressure accumulator into a digester containing fibrous material.

18. In. the digestion` of i'ibrous material, continuously pumping a stream of` chemical liquor to an accumulator chamber, passing the stream on its. Wayv to said chamber through an ejector nozzle extending into a l digester relief header, and thereby condensing gases and vapors from the relief Huid from a number of digesters, and thus mainl said header, also passing the pumped liquor on its way to? said accumulatorV chamber through a second injector nozzle, and utilizing suction created b the use of the second nozzle to withdraw t e gas from the top of the accumulator chamber, and to mix the last mentioned gas with the liquor flowing to said accumulator chamber.

19. In the digestion of fibrous material,

continuously pumping a confined stream of acid liquor to an accumulator chamber, passaccumulator chamber, and to mix the same with the flowing stream, and feeding liquor thus preheated and preconditioned from the accumulator chamber into a digester containing fibrous material; f\

20. An apparatus for use in digesting fibrous material, comprising a plurality of digesters, a header, valved branches connecting the -upper portions of the digestersv to said header, an injector nozzle extending into said header, an accumulator chamber, a conduit leading to the laccumulator from the portion of the header into which the nozzle extends, and means for forcing chemical liquor through said nozzle. a

21. Ali apparatus for use in digesting fibrous materia ,-comprising a plurality o digesters, a header, valved vbranc ing the upper portions of the digesters to said header, an injector nozzle extending into said header, an accumulator chamber, a conduit leading to the accumulator from the portion of the header into which the nozzle extends, and meansgfor continuously fo'rcing chemical liquor through said nozzle.

22. An apparatus for use in digesting fibrous material, comprising a plurality of digesters, a header, valved branches connecting the upper portions of the digesters to said header, an injector nozzle extending into said header, an accumulator chamber, a conduit leading to the accumulator from the portion of the header into which the nozzle extends, a pipe through which chemical liquor is forced to said nozzle, a second injector nozzle arranged in said pipe, and a conduit placing the upper portion of the accumulator chamber in communication with the pipe at a point in close proximity to the second nozzle, whereby suction created'by the use of the second nozzle, will cause gasto flow from the accumulator through said conduit.

23. An apparatus for use in digesting es connect-l 24. An apparatus for use 1n digesting brous material, comprising a plurality of digesters,4a relief header, valved branches con' necting the npper portions ofthe digesters to said header, an accumulator, a conduit connecting the header to said accumulator, an ing jector nozzle extending into the header at the point Where the latter 'oins said conduit, an acid liquor storage tank, and means for continuously forcing liquor from the storage tank to said nozzle. e B

25. An' apparatus for use in digesting 'fi- .brous material, comprising a plurality of di-A gesters, a relief header, valved branches connecting the upper portions of the digestors to said header, an accumulator, a conduit connecting the header to said accumulator, an injector nozzle extending into the header at the point where the latter joins said conduit, an acid liquor storage tank, and means for continuously forcing liquor from the storage tank to said nozzle, the last mentioned means including a pipe provided with a second injec- .l

tor nozzle, and a conduit connecting the upper portion of the accumulator to the last mentioned pipe at a point` adjacent to the second injector nozzle.

26. An apparatus for use in 4digesting fibrous material, comprising a plurality of digesters, a relief header for the digesters,

valved branches connecting thesupper portions of the digesters to said header, an injector connection interposed in said header, an accumulator, a conduit connecting said injector to said accumulator, a chemical liquor storage tank, a pipe joining the storage tank to said header and terminating in an injector nozzle which extends into said injector connection, and a pump interposed in the last mentioned pipe for forcing liquor from the storage tank to said nozzle.

27. An apparatus for use in digesting fibrous material, comprising a plurality of digesters, a relief header for the digesters, valved branches connecting the upper portions of the digesters to said header, an injector connection interposed in said header, an accumulator, a conduit joining said connection to said accumulator, a chemical liquor storage tank, a pipe joining the storage tank to said header and terminating in an injector nozzle which extends into said connection, a pump interposed in the last mentioned pipe for forcing liquor from the storage tank to said nozzle, and means for forcing hot preconditioned liquor from the accumulator to said digesters. 28. In an apparatus for use in digesting fi- `lorous material, a series of digesters, a high pressure header, a loW pressure header, valved branches connecting the upper portions of the digesters to said headers, an injector connection interposed in leach header, a low pressure accumulator, a conduit oining the injector connection of the low pressure header to said low pressure accumulator, a high pressure accumlator, a conduit joining the injector connection of ythe high pressure header tothe high pressure accumulator, means including an injector nozzle extending into the injector connection of the 10W pressure accumulator for forcing chemical liquor into the first mentioned conduit, and means including an injector nozzle extending into the injector connection of the high pressure header for forcing'chemical liquor from the low pressure accumulator into the second mentioned conduit. In testimony whereof, I hereto affix my signature.

PERCY W. NEIL. 

